In recent years our assumptions about the motivation of behavior have changed. From the view that all behavior is motivated by simple need reduction we have come to recognize that striving for competence is also a powerful motive. The major objective of this study is to investigate the development of mastery motivation in the first year of life. Three aspects of mastery have been distinguished: persistence in problem solving, in practicing emerging fine motor skills, and in securing sensory feedback from the physical environment. We are investigating the origins of mastery in the early parent-infant relationship and its continuity over time. The sample consists of 67 infants from middle income intact families, 34 boys and 33 girls. A variety of methods are being used--a series of twelve tasks developed to measure mastery motivation, an observation system involving continuous recording of mother-infant and father-infant interaction in the home, Bayley Scales of Infant Development and self-report measures of parent-infant interaction. Analyses will focus on continuity in mastery motivation between 6 and 12 months and on the relationship between specific aspects of the infant's early experiences with his parents and the development of mastery behaviors.